The present invention relates to a new and improved joint assembly, more specifically to a ball and socket type joint assembly. The joint assembly of the invention is one which may advantageously be utilized in a vehicle steering system, although it will be apparent that its use is not so limited. Known vehicle steering systems commonly include a plurality of components, e.g., a center link idler arm, pitman arm, etc., which are interconnected by ball and socket joints to permit multi-directional movement among them. Obviously, such ball and socket joints have any number of other well known uses aside from steering systems, generally whenever multi-directional movement is required between interconnected members.
A common problem for ball and socket joints, whether used in steering systems or other devices, is the necessity to maintain the various components of the joint assembly in proper operating position relative to each other despite the effect of wear on the components. Usually, this is accomplished by incorporating compressed expanders or springs into the assembly to "take up wear" by expanding as adjacent parts wear down, to maintain the wear-reduced parts in properly seated engagement. One problem is to provide for sufficient expander travel to avoid looseness even at maximum allowable wear. Another problem is to maintain dimensional tolerances of the various components within narrow limits so that misalignment of the assembled components and excessive friction therebetween is not sustained. Since the dimensional tolerances of assembled components accumulates ("tolerance stack up") individual tolerances must be held very close, which increases manufacturing cost. The use of both expanders and bearing elements to seat the stud head or ball increases the number of parts and aggravates the tolerance stack up problem.
The art has attempted numerous expedients to overcome these problems. For example, U.S. Pat. No. 3,667,789 shows a ball and socket joint including a belleville spring type expander engaging a bearing plate which is disposed in engagement with a ball element on a stud head. The problem of tolerance stack up of the parts is sought to be overcome by including a nonresilient, crushable component in the structure. This component is crushed upon assembly to take up dimensional variations in the assembled parts.
U.S. Pat. No. 2,528,221 shows a ball and socket joint wherein the ball or head portion is composed of two separable hemispherical components. The two components are maintained in seating contact with the socket cavity by means of an expander disposed internally of the assembled components.
The foregoing prior art attempts have to a greater or lesser extent typical shortcomings; one is the requirement to include extraneous parts of the assembly, which increases costs and complicates parts inventory and manufacturing procedures. Another is the limited amount of expander travel available to take up wear.